The object of the invention contained herein is a safety tool for supporting and holding a punch in a clamping system, used on the upper beam of a press-bending machine.
The invention has particular, but not necessarily exclusive, application in the press-bending machines sector.
There are various types of press-bending machines. They are used in the mechanical engineering industry, particularly for processing sheets of metal in order to obtain, for example, longitudinal sections with various profiles that can be re-worked with a press-bending cycle.
A press-bending cycle consists basically of a bending tool moving down vertically until it presses on a sheet of metal that is positioned on a work-bed, carries out the bending of the sheet, and returns to its original position. To carry out the aforementioned phases, the machine is made up of two parts. The first part, which is usually the upper part of the machine, is mobile, and a second part, which is usually a lower part, is static and positioned perpendicular to the upper part. Regarding the mobile part, during a typical work cycle, a punch, which is made with an interchangeable blade shaped according to the work to be carried out, carries out a vertical return movement by means of a hydraulic cylinder that lowers an upper beam which carries the punch (held in a clamping system) towards a lower beam, on which an interchangeable mould is positioned, followed by a pause and then its return upwards to the original position.
State of the Art
Generally speaking, most press-bending machines currently available on the market have interchangeable punches that make the machine more flexible in order to meet the wide range of requirements for the companies that use them.
According to the type of work to be carried out on the sheet of metal, there are two types of punches. The first one is made up of a single punch, that is, a single monolithic body with a linear blade, which is held longitudinally along the entire length of the upper beam by means of a single clamping system. The second type is made up of a divided or multiple punch, with various elements held by clamping systems to the upper beam. Each element is a single punch, and these punches may even be different from each other. While, with the first type, a single, continuous type of clamping system along the length of the upper beam is required to hold the punch, with the second type, a number of intermediate clamping systems are required according to the number of single punches to be held and clamped.
Regarding the punch itself, it is usually made up of a one-piece metallic body, with a square upper part called the shank, and a lower part that can be any of various shapes, which actually does the bending, perforating, or cutting. The shank is for attaching the punch to the upper beam, and it is the part on which the clamping systems operate. The clamping systems, operated by pneumatic or hydraulic cylinders, or other means of electro-mechanical systems, close one or more plates with a large surface area, thereby clamping and holding the shank of the punch.
The punch or punches have to be replaced more or less frequently, according to the type of work being carried out on the sheet of metal in question. This operation has to be carried out with the machine in a temporary state of arrest, and preferably with the upper beam at an accessible working height for the operator, to make the operation simpler.
To sum up, (see FIGS. 3, 3A and 3B that represent typical applications), whatever the shape of punch or punches used, there are three types of shanks available on the market that are clamped by one or more clamping means to the upper beam:
FIG. 3A shows the original type of shank, indicated as C1. This solution has been abandoned by all the manufacturers because of its lack of safety features. This type of shank has only one tooth that is square and has smooth walls. There is a support surface for the punch adjacent to the tooth, such as, for example, on the head of an clamping device on which the pushing force is distributed perpendicularly.
FIG. 3 shows the Standard-type shank, indicated as C2. This type, for punches with a pressing axis that is not in line with the support shank, has been standardised by all constructors of press-bending machines and punches and, compared to the first type, is characterised by the fact that it has a certain safety feature. This feature is made up of a seat or xe2x80x9cCxe2x80x9d-shaped continuous groove which runs transversally to the punch at the base and on one side of the shank, into which a holding tooth of the clamping device enters. The main function of this feature is to avoid the utensil dropping from its seat when the clamping means of the clamping device is released. A variation of the standard shank has a double safety groove. In this case, on each of the two sides of the shank, there is a groove which runs transversally, similar to the groove used for a single-type safety shank.
FIG. 3B shows the third type, indicated as C3. This type is not as common as the second type, and is only produced by some manufacturers. These xe2x80x9cpersonalisedxe2x80x9d shanks are designed to be used exclusively on certain makes of press-bending machines and are not interchangeable with other machines. A typical example is the GASPARINI(copyright) shank which, compared with the previous examples, is characterised by the fact that it has a wedge-shaped groove, into which the tooth of the clamping means enters and that, when released, allows the shank to be suspended from the upper beam in complete safety until it is manually removed by the operator.
Drawbacks
From the brief description above, it easy to imagine the main problems that the producers are trying to solve. First of all, there is the problem of the time required and the difficulties encountered when carrying out the operation of replacing the punch. This especially true when using the punch C2, which is the type most widely used, because the operator has to withdraw the utensil along one side. This operation is relatively simple if there is enough space at the side of the machine and if there is only one punch to be drawn out from the upper beam. The punch may be quite heavy, thus requiring more than one operator to withdraw it, or may require suitable lifting means such as a winch. The operation becomes much more difficult if the punch is divided. In this case, when the distance between the intermediate devices is less than the length of the punch, it is necessary to draw it out by withdrawing all the punches that precede it, with all the problems that are inherent with this type of operation.
All these operations have to be carried out with the machine in a rest position, which obviously implies that the cost involved will be proportional to the number of interventions that have to be carried out.
A second aspect that cannot be overlooked is the fact that the punches with safety features currently used are not automatically aligned. This problem is quite serious when high-precision components are being manufactured and where the split punches have to be perfectly aligned with each other. With the current technology, such alignment is almost impossible, resulting in operations carried out on the sheets of metal positioned below the punch that are not satisfactory according to current standards.
Amongst the solutions commonly used in order to resolve the first of the problems mentioned above, that is, withdrawing the punch sideways with respect to the upper beam, the insertion of the punch from below, and vice versa for its removal, is becoming common practice. In this case, in order to hold the groove of the safety feature that runs transversally to the standard-type shank, a wedge is used that is pressed into position in the groove by a spiral spring. This solution requires a considerable amount of effort by the operator to overcome the force of the spring, both when inserting or withdrawing the shank of the punch from the clamping means on the upper beam. The main drawback is given by the fact that the spring must be very strong in order to hold the punch in place when it is released, and must provide a strong pushing force perpendicular to the groove.
What is more, regarding the technique described, the force of the spring has to be calculated according to the length of the punch in order to make its movement easy. It is precisely the calculation of the force of the spring that presents a number of problems regarding the setting-up of this mechanism.
There is also a system that is defined as xe2x80x9cself-aligningxe2x80x9d by the manufacturer. This system has a closing plate with an inclined plane at the end that is tangential to the top of the side of the groove in the shank of the punch. When the plate is brought close, the plane goes against the top of the side of the groove, forcing the punch to go along the diagonal. Even though this solution seems original, it can only be used for punches made up of one single element, while in those cases where divided punches are used, it does not guarantee a uniform anchorage of all the elements, leaving play and leading to misalignment of the punches, which obviously leads to poor quality processing.
U.S. Pat. No. 5,022,256 Discloses a safety tool having a clamping device with a hooking tooth for holding a punch. It provides a resilient strip (6,32) having the hooking tooth (11) for safety purposes.
EP0779116A (AMADA GMBH), FIG. 2 discloses a quick clamping device for at least one tool (punch in the description) of a machine tool, in particular for one bending or edging punch of a bending or edging press, comprising a clamping member and a safety and hold means for the tool (punch), said clamping member being provided with an engagement strip which is pre-tensioned for engagement with a counter-recess in the tool shank and which is attached to be actuated by a central operating member in direction opposite to its tension. The above solution provides the use of an intermediate tool-engaging means (4) between the press-bending up-down-moving upper support (2) and said bending tool or punch and having the features of: hand-operated; missing in-line tool; unlocked positioning means in case of different thickness; dangerous tool extraction because one hand must be under the tool.
FR2339485A (COLLY PIERRE) discloses a lever hooking and locking means for a safety tool to be clamped as a solution close to the previous one. This feature does not provide high-precision and self-alignment and enables use with personalized bending-tools (punches) and side insertion only.
FR26916524 (TREILLET JEAN) discloses a safety tool device directly connected to the upper press-bending support, without intermediate locking safety device. This feature being manual with personalized tools (punches). Realization requiring a very high precision. Recovering in thickness being missing.
In the lever means solutions disclosed in EP0779116A and FR2339485A, a lever hooking and clamping means is disclosed, said lever hooking and clamping means having the fulcrum on the upper end, a clamping action being operated by closing said lever means, by acting on an intermediate portion of it, with an intermediate closing screw (in the EP0779116A Ref, 7,8 and in the FR2339485A Ref.3-6 assisted by side-counter-springs 7): In this way, the hooking of the bending-tool or punch is made operative, but with a force that is xc2xd of the closing force in its intermediate portion.
With regard to the above, and other techniques that are less widely used, the applicant believes that the means for holding the punch can be greatly improved with regard to operator safety.
This and other aims are achieved with a safety tool for supporting and holding at least one interchangeable punch having a shank with a first groove to an upper beam of a press-bending machine, comprising: a first clamping device adapted to be joined to the beam, the clamping device having a support body, a holding clip joined to the support body, and a safety hook joined to the holding clip, the safety hook having at one end a hooking tooth for engaging the groove of the shank of the punch, wherein the holding clip has a plurality of holding clip teeth adjacent the support body for engaging the safety hook and wherein a first one of the holding clip teeth, when engaging the safety hook, supports the safety hook and wherein a second one of the holding clip teeth, when engaging the safety hook, exerts a force on the safety hook, such that the safety hook is pressed against the shank.
Advantages
In this way, through the creative contribution of the system which leads to an immediate technical progress, various advantages are achieved.
In particular, the safety tool mechanism for holding the punch is extremely flexible since it can be applied to the upper beam on any press-bending machine currently used. It is extremely efficient and functional because it can be applied in all those situations where clamping devices used for clamping standard safety shanks are foreseen.
Going into detail, there are considerable advantages for the operator of the machine, who can carry out removal of the punch from the upper beam in complete safety with a very simple operation that, above all, allows the operator to perceive the moment in which the punch is unhooked and released from above to below slightly in advance. At the same time, the insertion of the chosen punch in the intermediate positions along the beam from below can be performed, which is an operation that can be carried out very quickly and without any particular effort by the operator.
Regarding safety, each punch is moved laterally using either one or both hands, and unlike in the previous systems, along the line of the press, thus offering maximum protection against work accidents.
Among the advantages that are worthy of note, there is an unrivalled self-aligning capacity of each punch with the other split punches along the horizontal and vertical axes when using this system, so that extremely precise pressing operations can be carried out and thus considerably improving the overall quality of the finished product.
The elimination of play and the stability of the punch after closing the holding clip further improve the quality of the process. The system, right from the initial contact with the sheet of metal to be processed, eliminates the small movement along the vertical axis of the punch that is perceived when using traditional clamping systems. Furthermore, since the system has no play, the operator has an impression of working with a reliable tool, thus leading to a natural sensation of operating under safe working conditions.
The overall safety is considerably improved since the punch, when released, can not fall even if it oscillates laterally, whether in one direction or another, as may accidentally occur in the systems described previously.
Because of the presence of the hooks, which are more or less equal in length to the clamping devices, the punch is hooked more safely because, if one or more of the hooks are no longer operational, there are the remaining hooks that hold the punch very efficiently.
Furthermore, because of the adoption of certain measures, there is a uniform holding of the punch, which is distributed evenly along the entire surface of the shank of the punch. At the same time, by modifying the mechanism for operating the holding clip, the hold is also more uniform when only one clamping system is used to clamp a single punch to the upper beam.
These and other advantages will be explained in the following detailed description and attached drawings of various applications of the system, which are to be considered simply examples and not limitations of the system.